Railway traffic controlling system



Sept. 29, 1936.

s. N. WI GHT RAILWAY TRAFFIC CONTROLLING SYSTEM Filed July 15, 1932Patented Sept. 29, 1936 PATENT OFFICE RAILWAY TRAFFIo CONTROLLING SYSTEMSedgwick N. Wight, Rochester, N. Y., assignor to General Railway SignalCompany, Rochester, N

Application July 15, 1932, Serial No. 622,645

21 Claims.

The present invention relates to railway traflic controlling systems,and more particularly to a communicating means in such a system wherebya single circuit extending to a remote point may be used for thetransmission of a plurality of messages.

In controlling a distant railway traffic controlling device fromacentral point, it is expedient to employ a minimum number of line wiresextending from the control point to the various distant locations, bothbecause of the cost of the line wire as well as the increased cost ofmaintenance of a larger number of wires over the considerable distancesnecessary to extend the line circuits. It is found convenient in suchsystems to not only provide means for controlling distant devices, suchas switches and signals, but to receive indications at the control pointof the operated position of such devices, and also of the presence of atrain on certain sections of track, which consequently enablesconsiderable saving to be made by multiplying the use of each circuitboth for the transmission of controls and indications.

In view of the above and other considerations, it is proposed inaccordance with the present invention to provide a communicating meansin a railway traffic controlling system whereby a distant trafficcontrolling device may be controlled by selectively applying continuouscurrent energy to a single line circuit, and whereby one or moreindications of the condition of the same or different devices may betransmitted to the control point over the same line circuit by changingthe continuity of the control energization. It is also contemplated thata portion of the present scheme may be employed for various otherrailway signalling purposes in which a very simple and reliableoscillating contact means is required, in as much as it is proposed tooperate the present contact oscillating means with a single magneticstructure and a single armature.

Other objects, purposes and characteristic features of the presentinvention will become apparent as the description thereof progresses,during which, references will be made to the accompanying drawing, inwhich:-

Fig. 1 diagrammatically shows a typical arrangement of the presentinvention for controlling a distant signal, and for indicating at thecontrol point the condition of such signal and the presence of the trainin an associated track section, and

Fig. 2 is a modified form of the present invention arranged to control adistant signal and to receive indications of the condition of the signalat the control point.

Fig. 3 diagrammatically shows a modified use of a portion of theinvention shown in Fig. 2.

A portion of a control panel is diagrammatically shown in theaccompanying drawing, which has a straight section of miniature track MTcorresponding to a distant section of actual track T, which track T hasa signal S governing trailic movements thereover and an associatedindicating light SK is shown on the control panel for displaying anindication when the signal S is clear. A means for setting up thecontrols for signal S is shown on the control panel by a rotary controlbutton SGL, which is shown in its signal at stop position 3 and isoperable clockwise to a position e which sets up a control to clear theeast bound signal S.

The various relays at both the control point and the distant signallocation are shown conventionally on the accompanying drawing, and therelays having heavy base lines, such as relays K, KK and SLP, have slowacting characteristics, or they are so constructed that the timeconsumed in releasing their armatures is considerably longer than thetime consumed in picking up. An impulsing relay P is shown'on thedrawing as a neutral relay having its energizing circuit carried throughits own toggle contact, and it is to be understood that this arrangementis shown merely as a simple way of indicating a means for periodicallyoscillating a 'contactto alternately open and close a circuit forsubstantially equal periods of time, and that in practice a morepractical means will probably be employed. The relay P as shown isarranged to open its back contact I when energized but shortlythereafter the energization is interrupted by the-operation of thetoggle contact and the back contact I is again made followed by thedropping 40 of the toggle contact, or in other words; oscillation of thecontact I is eifected by the lag in the operation of the toggle'contactwhich controls the energization of the relay. The relay shown in O. S.Field Patent No. 1,969,065 issued August 7, 1934 may be substituted forthis relay P in a manner which will be obvious from a study of thepatent.

A source of energy for the line circuit is shown as battery B, and it isunderstood that the wire L is the line wire for the particular distantsignal shown herein whichmay be located a consider l able distance fromthe control point and also that the wire C may be a common line wire forthe control or indicating circuits of other traffic C011.

trolling devices. A local source of energy is required at each location,which is not shown herein but the symbols and are used to indicate theopposite terminals of such a source.

Considering now that it is desired to clear the east bound signal S toallow a traflic movement onto the track section T, the signal controlbutton SGLis rotated clockwise to a position e which energizes the linecircuit from the battery B as follows:from the terminal of battery B,wire 5, contact 6 of the rotary signal control button SGL in its signalclear position e, wire I, through the windings of relay GP, line wire L,front contact 8 of relay TR, wire 9, back contact I of relay P, wire I0,throughthe winding of relay SLP, wires II and I2, and returning -to theterminal of battery B by the common line wire C and wire I3. Thecompletion of this -circuit allows a continuous current to flow throughthe line circuit thereby picking up relay SLP which is efiective'toclear signal S by means which is merely indicated herein by contact I4of relay SLP. The circuit effective to clear signal S is of coursedependent in the usual manner upon local blocksignalling circuits, whichhave herein been omitted to simplify the disclosure, but it is to beunderstood that the closing of front contact I4 completes a circuitwhich is efiective to conditionsignal S for displaying a clear signalindication whenever the way is clear ahead. The line being thusenergized also picks up the relay GP at the control point whichcompletes a circuit at its front contact l8 to pick up the slow actingrelay KK.

When the signal S has thus displayed a clear indication,-an energizingcircuit is closed to operate the impulsing relay P, which circuit hasdiagrammatically been shown as completed through a contact I5 operatedin accordance with the position of the semaphore blade of signal S, butit is to be understood that any circuit closing means maybe substitutedfor this contact I5 which is closed whenever the signal S displays aclear indication. This energizing circuit for the impulsing relay P maybe traced from contact I5 in its dotted or signal clear position, wireI6, through its own toggle contact, through its operating winding to andis effective in the manner previously described to alternatelyopen andclose its-back contact I at substantially equal periods of time.

The back contact I of relay P being in series with the energizingcircuit for the control line previously traced is now effective tochange the continuous line energization, to impulses which are separatedby corresponding periods of de-energization, which obviously causes therelay GP at'the .control point to operate its armature in synchronismwith theoperation of,relay P, in as much as this relay GP is constructedwith quick acting characteristics. This oscillating motion of thearmature of the relay GP is obviously effective to hold up theslow'releasing relay KK during the energized period of the line over thecircuit:previously mentioned, and during the de-energized period, whichis shorter than the releasing time of :the relay KK, a circuit iscompleted to energize relay K from back contact I8 of relay GP, wire I9,front contact 20 of relay KK, wire 2'I, through the windings of relay Kto The relay'K having similar characteristics to the relay K is pickedup during the de-energized period of the line and is not released duringthe energized period and consequently both relays K and KK remain pickedup as long as the impulsing of the line circuit continues.

An energizing circuit for the indicating light SK is now completed fromfront contact 23 of relay KK, wire 24, front contact 25 of relay K, wire26, through a lamp filament of the indicating light SK to In this mannera signal control relay is energized over a line circuit to clear itssignal, and when such signal has operated to a clear position, anindication of such operation is returned to the control point over thesame line circuit.

Considering now that an approaching train accepts the clear signal S andenters the section of the track-in front of the signal S, a track relayTR arranged in the conventional manner is dropped thereby interruptingthe impulsing energization of the line circuit at contact 8 which dropsrelay GP at the control point. The dropping of relay TR also completes acircuit for holding up the signal control relay SLP from through stickcontact 23 of relay SLP, wire lI, through the winding of SLP, wireIIL'back contact I of relay P, wire 9, back contact 8 of relay TR to Thedropping of relay GP is efiective at the control point to de-energizerelays KK and K thereby energizing the indicating light OSI with thesignal control button SGL in the clear position over a circuit from backcontact 29 of relay GP, wire 30, back contact SI of relay K, wire 32,contact 33 of the signal control button SGL in its signal clearposition, wire 34 through a lamp filament of the indicating light 051 toIn this manner, the presence of a train on a track section is indicatedat the control point by the de-energization of the same line circuitused for the transmission of signal controls and indications, and it maybe seen that this de-energization is only effective to indicate suchtrack section occupancy whilethe signal control lever SGL is in aposition to effect the clearing of the signal S.

The modified form of the present invention shown in Fig. 2 isillustrated in the same arrangement as Fig. 1, except that a transformerTF is employed at the control point and a differentially wound relay Fis used at the signal location, which relay F has two windings, A and B,arranged to produce equal and. opposite flux thereby releasing thearmature when both are energized. It will also be noted that theindication of the track circuit has been omitted in Fig. 2, or thisarrangement may be considered as a modified means for changing thecharacter of the control energization of the line circuit for thetransmission of indications.

The control of the signal S in Fig. 2 is accomplished in the samegeneral manner as in Fig. 1, or the moving of the signal control buttonSGL to position 6 causes the line circuit to pick up relay 'SLP from theside of battery B, over wire 36, contact 3'? of signal control buttonSGL inposition e, wire 38, through the primary winding 39 of transformerTF, line wire L, wire 40, through winding B of relay F, wire 4I, throughtheoperating winding of relay SLP wires 42 and 43, and returning to theside of battery 13 by the common wire C and wire 14. This eifects theclearing of the signal S in the same general manner as described inconnection with Fig. 1,

and when signal S is operated to its clear position, the contact I5closes a circuit which energizes winding A of relay F in parallel withthe winding of relay SLP which parallel circuit/may be traced over thepreviously traced line energizing circuit to line wire L, and from thereover wire 45, front contact 46 of relay F, wire 41, through winding A,wire 48, contact IS in its dotted or signal clear position, wire 49 tothe opposite side of relay SLP and again joining the previously tracedline energizing circuit.

When this parallel circuit around relay SLP is closed it is obvious thatan increased amount of current flows through the line circuit at thecontrol point, but as previously described, when the winding A and thewinding B of relay F are both energized, the flux acting to hold frontcontact 46 closed is neutralized thus causing the parallel circuitthrough winding A to be opened at front contact 46, and the current inthe line circuit is again reduced to its normal lower value at thecontrol point. It may be seen that 'the relay F will again pick upshortly after winding A has been de-energized and continues to operatein this oscillating manner to periodically open and close its contact 46as long as the signal contact I 5 is in the horizontal position, whichoscillation of the contact 45 creates a pulsing current in the linecircuit at the control point.

This pulsing current in the line circuit is effective at the controlpoint to induce an alternating current voltage in the secondary winding50 of the transformer TF, which voltage picks up the sensitive relay Kconnected thereacross as shown. The picking up of relay K closes anenergizing circuit for the signal indicating light SK from front contact5| of relay K wire 52, through a lamp filament of the indicating lightSK to This modified indicating system may then be said to comprise ameans for changing the steady control energization to a pulsingenergization which effects a means at the control point which is notresponsive to the steady energization, such as a. transformer and relayarrangement.

Another use for the relay F has been shown in Fig. 3, and has forexample been illustrated as alternately energizing two lights H and Hwhich may be the signal lights of a highway crossing signal system, orit is obvious that various other devices may be alternately controlledin a similar manner. The operation of relay F in Fig. 3 is much the sameas described inconnection with Fig. 2, or as may be seen, the closing ofback contact 55, which may be any controlling means such as a trackrelay, energizes the winding B but during the time consumed by thepicking up of relay F, which time in most cases will be madecomparatively long, the light H is energized through back contact andback contact 56 of relay F. However, when the relay F picks up thecircuit is changed to energize lightH instead of light H at frontcontact 56, and the winding A is also energized at front contactv 56 toneutralize the flux of winding B and again drop the relay armature.

A control and indication communicating means for a railway trafficcontrolling system has thus been provided which permits the control of adistant trafiic controlling device over a single line circuit byselectively applying continuous current energy to the line circuit, andalso permits .an indication to be returned to the control point, such asa particular condition of a traffic controlling device, by alternatelyopening and closing this circuit at the distant location to change thecontinuous current to impulsing current. In other words,-a continuousenergization of the line circuit is ineffective to a certain arrangementof relays at the control point, but when an oscillating contact at thedistant location changesthiscontinuous'energization to energy impulsesseparated bycorresponding periods of de-energization, the relayarrangement at the control point is effective to. set up .a conditionforregistering the condition of the indicated device.

This relay arrangement at the control point is made responsive topulsing current only by a relay arranged to pick up on the energizedperiod and a second relay arranged to pick up on the deenergizedperiod,.with both of these relays so constructed that their releasingtime is substantially longer than their pick-up time, so that whenpicked up during one of the aforesaid impulsing periods they will notrelease on the following opposite periods. A second indication may alsobe transmitted either during the continuous or the impulsingenergization of the line circuit by continuously interrupting this'energization or deenergizing'theline circuit at the distant locationwhich is eifective at the control point to register this secondindication providing the control button is in a position ordinarilyeffecting the energization of the line circuit.

A modified form of this scheme has also been disclosed which differs inthat the continuous control current is changed from the transmission ofan indication to pulsing current by applying alternate periods of anincreased amount of current by means at the distant location, instead ofinterrupting the current in this period. The indication registeringapparatus at the control point in the modified arrangement is maderesponsive to the pulsing current only by a transformer having itsprimary winding in series with the line circuit and obviously thecontinuous control current does not induce current in the secondarywinding thereof but the pulsing indicating current induces suliicientalternating current in this secondary to pick up a sensitive alternatingcurrent relay connected across the secondary winding. The oscillatingrelay which is employed at the distant location to periodically increasethe line current may be used for various other purposes as has beenshown and described in Fig. 3. This simple arrangement employs only asingle magnetic structure of the conventional design and a single frontand back contact may be employed to effect oscillation of the relayarmature as Well as to control various external circuits.

The above rather specific description of one form of the presentinvention is given solely by the way of example, and is not intended inany manner whatsoever in a limiting sense. It is also to be understoodthat various modifications, adaptations and alterations may be appliedto meet the requirements of practice, without in any manner departingfrom the spirit or scope of the present invention, except as limited bythe appended claims.

Having thus described my invention, what I claim is:--

1. In a railway trafiic controlling system, a control point, a distanttraffic controlling device tending to assume a predetermined condition,a line circuit extending from said control point to the location of saiddistant traflic controlling device, means at the control point forselectively applying continuous current energy to said line circuit,responsive means at the location of the traflic controlling deviceeffective to control said traihc controlling device to a differentcondition in response to the energization of the line circuit and onlyso long as such energy is applied, means at the distant location for"impulslng the continuous energization of the line circuit during theexistence of said difierent condition of the traflic controlling device,(and means at the control point responsive to the impulsing energizationof said line circuit to indicate said diiierent condition of the distanttraflic controlling device.

2. In a railway traffic controlling system, a control point, a normallydeenergized distant trafiic controlling device, a line circuit extendingfrom said control point to the location of said distant trafliccontrolling device, means at the control point for selectively applyingcontinuous current energy to said line circuit, responsive means at thelocation of the traific controlling device effective to energize saidtrafiic controlling device when said iline circuit is energized, meansat the distant location for impulsing the continuous energization of theline circuit during the energized condition of said traffic controllingdevice, and means at the control point responsive to the impulsingenergization to indicate said energized condition of said distanttraflic controlling device.

3. In a railway traific controlling system, a control point, a distantlocation, a line circuit connecting said control point and said distantlocation, means for controlling a tra'flic controlling device at thedistant location by selectively applying continuous current energy tothe line circuit at the control point, means at the distant location forperiodically opening and periodically closing said line circuit inresponse to the existence of a first static condition of the trafiiccontrolling device, means at the control point responsive only to theline circuit impulses created by said openings and said closings of saidline circuit to indicate said first static condition of the trafficcontrolling device, means for steadily opening said line circuit inresponse to the existence of a second static condition at the distantlocation, andmeans responsive to said steady opening of the line circuitto indicate said second static condition at the control point.

4. In a railway trafiic controlling system, a control point, a distantlocation, a line circuit connecting said control point and said distantlocation, a signal, control means for said signal rendered effective byselectively applying continuous current energy to the line circuit atthe control point, means at the distant location for periodicallyopening and periodically closing said line circuit in response to theexistence of a first static condition of said signal, means at thecontrol point responsive only to the impulses created by said openingsand said closings of said line circuit to indicate said first staticcondition of said signal, means for steadily opening said line circuitin response to the-existence of a second static condition at the distantlocation, and means responsive to said steady opening of the linecircuit to indicate said second static condition at the control point,when said control means is operated to a position for applying energy tosaid line circuit.

5. In a railway trafiic controlling system, a control point, a distanttraflic controlling device, a line circuit connecting the control pointand the distant traffic controlling device, means for controlling thetraffic controlling device by selectively applying direct current energytosaid line circuit at the control point, means at the distant trafficcontrolling device for pulsing the energization of the line circuitduring a certain condition of the controlling device -byintermittentlyLincreasing the direct current energiza- 'tion of thelinegand means at the control point responsive to said pulsing linecircuit energization to visually indicate said certain condition of theitraffic controlling device.

6. A railway traffic controlling system, comprising, a control point, adistant location, a line circuit connecting the control point and thedistant location, a control switch arranged to selectively energize theline circuit at the control point, a signal control relay at saiddistant location in'series with said line circuit, an oscillating meansarranged to periodically open and close said line circuit when a clearindication is displayed by the signal controlled by said control relay,two slow releasing relays at the control point, one of said slowreleasing relays picking up during the open circuit line period and theother during the :closed line circuit period, and signal indicatingmeans at the control point energized when'both of said slow releasingrelays are picked up.

7. -A railway traflic controlling system, comprising acontrol point, adistant location, a line circuit connecting the control point andthe-distant location, 'a control switch arranged to selectively energizethe line circuit at the control point, a signal control relay at saiddistant location in series with said line circuit, an oscillat ing meansarranged to periodically open and close said line circuit when a clearindication is displayed by the signal controlled by said control relay,-two slow releasing relays at the control poin't,one of said slowreleasing relays picking up during the open line circuit period and theother during the closed line circuit period, signal indicating means atthe control point energized when both of said slow releasing relays arepicked up, a track relay at said distant location arranged to open saidline circuit and to stick up said signal control relay when a trainoccupies a particular track section, and track circuit indicating meansat the control point energized when said control switch is in its lineenergizing position and the line circuit is de-energized.

8. In combination, a local control oflice, a distant control point, atrafiic controlling device at said control point normally tending toassume a predetermined condition, a control circuit connecting saidofiice and point and for causing said device to assume another conditionif and only when said control circuit is energized either continuouslyor intermittently, means for continuously energizing said controlcircuit from said local office, means 'for intermittentlybreaking saidcontrol circuit when said device assumes said another condition, and anindicator at said local office rendered active when said control circuitis intermittently energized.

9. In combination, a local control ofiice, a distant control point, atraflic controlling device at said control point normally tending toassume a predetermined condition, a control circuit connecting saidofiice and point and for causing said device to assume another conditionif and only when said control circuit is energized either continuouslyor intermittently, means for continuously energizing said controlcircuit from said local office, means for intermittently breaking saidcontrol-circuit when said device assumes said another condition, anindicator at said local ofiice rendered active when said control circuitis intermittently energized, a second indicator rendered active whensaid control circuit is open at said control point for an appreciabletime, and other means at said control point for opening said controlcircuit for such appreciable time.

10. In combination, a local control ofiice, a distant control point, atrafiic controlling device at said control point normally tending toassume a predetermined condition, a control circuit connecting saidoflice and point and for causing said device to assume another conditionif and only when said control circuit is energized either continuouslyor intermittently, means for continuously energizing said controlcircuit from said local ofiice, means for intermittently breaking saidcontrol circuit when said. device assumes said another condition, anindicator at said local office rendered active when energized, two slowacting relays one relay of which is energized when said control circuitis energized and the other of which is energized when said one relayassumes its energized condition and said control circuit is deenergized,and an energizing circuit for said indicator including in series frontcontacts of said two relays.

11. In combination, a local control office, a distant control point, atralilc controlling device at said. control point normally tending toassume a predetermined condition, a control circuit connecting saidofiice and point and for causing said device to assume another conditionif and only when said control circuit is energized by either acontinuous or an undulating current, means for energizing said controlcircuit from said 10- cal oflice by continuous current, means forintermittently changing the resistance of said control circuit at saidcontrol point to change said continuous current to an undulating currentwhen said device assumes said another condition, and an indicator atsaid local office rendered active in response to undulating current insaid control circuit.

12. In combination, a local control oflice, a distant control point, atraflic controlling device at said control point normally tending toassume a predetermined condition, a control circuit connecting saidofiice and point and for causing said device to assume another conditionif and only when said control circuit is energized by either acontinuous or an undulating current, means for energizing said controlcircuit from said local oifice by continuous current, an auxiliary relayat said control point having a main winding and a bucking winding withits main winding included in said control circuit, a. circuit branch forsaid bucking winding to neutralize the effect of said main windingincluding a front contact of said auxiliary relay and a contact closedwhen said device assumes said another condition, whereby said frontcontact is intermittently opened and the resistance of said controlcircuit is intermittently changed when said device assumes said anothercondition, and an indicator at said local oifice responsive to theundulation of current in said control circuit.

13. In a railway trailic controlling system, a control point, a distanttraffic controlling device tending to assume a predetermined condition,a line circuit extending from said control point to the location of saiddistant trafiic controlling device, means at the control point forselectively applying continuous current energy to said line circuit,responsive means at the location of the traflic controlling deviceeifective to control said trafiic controlling device to a difierentcondition in response to the energization of the line circuit and. onlyso long as such energy is applied, means at the distant location forchanging the character of the continuous energizationof the line circuitduring the existence of said different condition of the trafliccontrolling device, and means at the control point responsive to thechanged character of energization of said line circuit to indicate saiddifferent condition of'the distant traflic controlling device. f

14. In a railway trafiic controlling system, a control point, a distanttraflic controlling device tending to assume a predetermined condition,a line circuit extending from said control point to the location of saiddistant trafiic controlling device, means at the control point forselectively applying continuous current energy to said line circuit,responsive means at the location of the trafiic controlling deviceefiectiveto control said trafiic controlling device to a differentcondition response to the energization of the line circuit and only solong as such energy is applied, means at the distant location forchanging the degree of the continuous energization of the line circuitduring the existence of said different, condition of the trafficcontrolling device, and means at the control point responsive to thechanged de-' gree' of energization of said line circuit to indicate saiddifierent condition of the distant traific controlling device.

15. In a railway traflic controlling system; a line circuit extendingbetween a control office and an outlying field station; means at thecontrol ofiice for at times energizing said circuit; a neutral relay atthe field station which is picked up whenever said line circuit isenergized; a traflic controlling device operated toa particular staticcondition whenever and only when" said neutral relay is picked up;meansat the field' sta tion for impressing a series of impulses-onsaidline circuit without-dropping said neutral'relay, said means beingeffective only when said traffic controlling device is operated to saidparticular static condition; and means at the control office responsiveto the impulses on said circuit to indicate said particular staticcondition of said traffic controlling device.

16. In a railway trafiic controlling system; a line circuit extendingbetween a control office and an outlying field station; manuallycontrollable means for selectively energizing said line circuit; atrafilc controlling device at the field station: transmitting means atthe field station for impressing a series of impulses on said linecircuit only when said trafiic controlling device is in a particularstatic condition; a relay at the field station responsive to theenergization of said line circuit either when steadily energized or whenimpulsed by said transmitting means to continuously actuate said trafliccontrolling device to said particular static condition; and an indicatorin said control ofiice responsive only to the impulsing of said linecircuit to thereby indicate said particular static condition of saidtrailic controlling device.

17. In a railway trafiic controlling system, a traffic controllingdevice at a field station, a line circuit connecting the field stationwith a central oflice, control means at the central oflice forselectively energizing said line circuit to thereby control said trafiiccontrolling device, means at the field station for continuouslyimpulsing said line circuit when said trafiic controlling device is in aparticular condition for a prolonged and indeterminate period of time,impulse responsive means at the central ofiice responsive only toimpulses on said line circuit, and an indicator controlled by saidimpulse responsive means and steadily illuminatedwhile there areimpulses on said line circuit.

18. In a railway traflicw controlling system, a traflic controllingdevice. at a field station, a line circuit connecting the field stationwith a central oflice, control means at the central oifice forselectively energizing said line circuit, means at the field stationresponsive to the selective energization of said line circuit forcontrolling said traffic controlling device, transmitting means at thefield station for causing recurring variations in the degree ofenergization of said line circuit while said traflic. controlling deviceis in a particular static condition, and means at the central ofliceresponsive to the energization of said line circuit only when its degreeis recurringly varied by said transmitting means.

19. In a railway traffic. controlling system, a trafiic. controllingdevice at.a field station, a line circuit connecting the field stationwith a central ofii'ee, manually. operable control means at the centraloifice for at times continuously energizing said line circuit, means atthe field station responsive to the continuous energization of said linecircuitifor. actuating said traffic controlling device, transmitting.means at the fieldv station for causing recurring variations in thedegreevof said continuous energization of said line circuit while saidtraflic controlling device is inv av particular static condition,.anelectro-responsive means capable of assuming. av normally biasedposition or. an actuated. position,. and means at. the central ofliceresponsive to the energization of said line. circuit. only when itsdegree is recurringly varied by. said transmitting. means to cause saidelectro-responsive means. to assume an actuated position.

20. In a. railway traflic controlling system, a

line circuit. connecting afield station with a central oflice, manuallyoperable means at the central office for energizing or deenergizing saidline circuit, means at the field station for impulsing said line circuitfor an indeterminate period of time when said line circuit is energizedby said manually operable means, means at the field station steadilymaintained actuated in response to the energization of said line circuitirrespective of whether such energization is steady or is impulsed, anindication relay in the control office, and circuit means for energizingsaid relay only when said line circuit is impulsed, said indicationrelay remaining picked up throughout such impulsing period, an indicatorlamp, and an energizing circuit for said indicator lamp including afront contact of said indication relay, whereby said indicator lamp issteadily illuminated While there are impulses on said line circuit.

21. In a railway traflic controlling system, a normally deenergized linecircuit extending from a control point to a distant traflic controllingdevice, a neutral relay included in series in said line circuit at. theremote point for governing the operation of the traflic controllingdevice, a manually operable contact at the control point for connectinga source of energy in series in said line circuit whereby said linecircuit is continuously energized or deenergized dependent upon the openor closed position of said contact, means at the remote point for attimes causing recurring variations in the continuous current flow insaid line circuit while said manually operable contact is closed, andelectroresponsive means at the control. point steadily actuated inresponse to said recurring variations in the current in said linecircuit.

SEDGWICK N. WIGHT.

